Most difficult aspect of English spelling?

What's the most difficult aspect of English spelling? Tell everyone your thoughts on this. And it will also help me know what's most useful to address on The Spelling Blog.

We'd love to know. Tell us in the AnswerGarden word cloud below by either clicking on an existing word or phrase that you agree with or writing something new in the box. You can only contribute once every 24 hours. And you have to keep it short. (If you want to say more please leave a Comment in the usual way.)

Trickiest thing about English spelling... at